In print media production, after a printing device a more or less elaborate post-processing is often implemented for a printing substrate web, for example a paper web. The finished printer products are there produced from the printing substrate formats used for the printing. Post-processing machines can be, for example, cutters, binders, folders, or stackers.
In electrophotographic printing, the toner images (generated on the printing device in the printing device) of the images to be printer are fixed and thus connected with the printing substrate. This method is known (see WO 01/98840 A2, which is herewith incorporated into the disclosure) and is therefore not explained further here. The fixing can occur in various ways, for example via roller fixing under pressure and heat or via radiation fixing. For the individual techniques, reference is made to the already-cited WO 01/98840 A2. In the fixing, the printing substrate web is thus exposed to heat or pressure, with the consequence that its properties such as, for example, dampness and sliding properties are negatively influenced. In particular, however, poor sliding properties of the printing substrate can lead to the fixed toner layer being mechanically damaged or smeared in the machines of the post-processing. These types of damages can lead to accumulations of toner particles at exposed machine parts, which can in turn lead to unwanted toner deposits on the printing substrate web. From WO 01/98840 A2 it is known to improve the post-processing of the printing substrate web in that the printing substrate web is moistened, such that the loss of dampness caused by the printing is compensated for. Water is normally used as a means for moistening.
In general, however, for an acceptable print quality, contamination, particularly on the printing substrate web, must be prevented at the machines, in particular for the post-processing. However, it is not sufficient to moisten the printing substrate web corresponding to WO 01/98840 A2. Rather, its sliding properties must also be improved.
In the transport of a printing substrate web from an electrographic printing device to post-processing machines, problems occur when the printing substrate web must be transported on the transport path with different speeds. In order to then prevent a web break or too-large web loops of the printing substrate web, reserve buffers are provided for the printing substrate web. An example of this results from U.S. Pat. No. 5,685,471. Between the printing device and post-processing machines (output stacker for the printing substrate web), reserve buffers are necessary in order to have sufficient reserve of printing substrate web upon starting and stopping of the print device in order to be able to correspondingly activate or deactivate (in terms of their functionality) the post-processing machines with temporal decoupling. In particular via the withdrawal for the pages of suitable re-printing necessary in the printing device, in particular in color printing, due to the start launch, a reserve amount of the printing substrate web must be held until the printing speed has been achieved, in order to prevent a tear of the printing substrate web.
It has been proposed to solve this problem with the aid of what is known as a dancing roller, a roller lying on the printing substrate web such that it is freely guided. When, in operation, a slack of the printing substrate web (a sag of the printing substrate web) occurs, this is drawn into the reserve buffer by the weight of the dancing roller and thus a loop is formed.
Further devices with which, for example, properties of the printing substrate web negatively influenced by the printing are corrected are, for example, a smoothing device (glossing device) or a cooling device. The smoothing device is customarily arranged after the fixing station in the printing device (EP 0 758 766 B1) and comprises at least one smoothing roller that is pressed on the printing substrate web. With a cooling device, the printing substrate web can be cooled before this arrives at the post-processing machines. Finally, the printing substrate web must be moved to the post-processing machines with the aid of a transport device.